A deliveryman was taken to hospital for gas inhalation and is expected to make a full recovery, police said.

Officers established a security perimeter around the plant, which is located in an industrial park. Workers in nearby buildings were evacuated, but employees at Olin Chlor Alkali were told to remain at the chemical plant, police said. None of the workers at the plant were injured.

Witnesses said they saw a yellow cloud in the air after the explosion. Witnesses also reported an overpowering smell immediately after the incident. The smell lingered in the air through the afternoon, CTV Montreal's Max Harrold reported.

Environmental officials will test the air quality before allowing workers to return to the area.

With files from CTV Montreal

Photos

One man was injured as a tank containing chlorine exploded at Olin Chlor Alkali Products plant in Becancour, Que., on June 25, 2014.